Aircraft tire with reinforcement insert

ABSTRACT

An aircraft tire 10 has at least one circumferentially extending reinforcement insert. At least one reinforcement insert 90 is located on one side of the tire. Each insert 90 preferably has two cord reinforced members 91,92 having bias angled cords. The cords are equal but opposite in orientation relative to the cords of the adjacent member. The pairs of reinforced members 91,92 extend from the bead portion 18,20 and terminate in a radially upper portion of the sidewall 14A,16A. Each pair of reinforced members 91,92 is interposed between the carcass plies 36,37,38,39,40,41, and the sidewall of the tire 10. In a preferred embodiment of the invention the inserts 90 are located on only one side of the tire. Alternatively, the inserts can be symmetrically added to each side of the tire.

This is a division, of application Ser. No. 08/363,086 Dec. 23, 1994 nowU.S. Pat. No. 5,538,063.

BACKGROUND OF THE INVENTION

This invention relates to pneumatic tires and more particularly to anovel carcass structure specifically for use in aircraft tires.

An aircraft tire is subjected to extreme operating conditions whichinclude very high internal pressure, high speeds in excess of 300kilometers per hour, and very high deflections. During taxiing andtakeoff, the deflection may be more than 30%, and on landing 45%deflection or more under impact conditions. These extreme pressures,loads and deflections put the sidewall between the shoulder of the tireand the bead to severe tests. The high pressure and loads place the plycords under severe tensile loads. The cords in the plies, particularlyin the lower sidewall area, are frequently mechanically fatigued due tohigh heat buildup near the beads while the aircraft is taxiing or duringtakeoff.

In the prior art, it has been conventional to increase the number ofplies of the tire to increase rigidity and to decrease deformation underload. Also much work has been directed to reinforcing the ply turnupportion of tires to improve durability.

U.S. Pat. No. 5,105,865 by Togashi et al. describes these conventionalsolutions and proposes that the durability of the tire can be improvedby avoiding bending deformations of the ply surfaces. The patentdescribes a tire curvature that permits an increase in durability to beachieved with no increase in weight.

U.S. Pat. No. 4,029,137 by Robert Suydam teaches that an improvement indurability can be achieved by a novel wrapping of the ply structureabout the beads. This invention also improves durability withoutincreasing weight.

In British Patent GB 2 087 806 to Kaisha, a bias aircraft tire isdisclosed wherein cords of the carcass plies are spaced further apart toachieve improved durability.

In addition to the normal loading conditions of aircraft tires militaryaircraft, in particular naval airships often are required to land on thedecks of aircraft carriers. The landings are routinely harsh and rapiddue to the shortened landing area. To stop the aircraft, an arrestorcable is employed. The nose wheel or main landing gear wheel of theaircraft impacts this 15/8 inch diameter arrestor cable on landings andcan severely damage the tire. On the F/A-18E/F naval aircraft the maintire can see a camber angle of 10.2°. This means that one sidewall willtake the initial impact at about five times the normal rated load. Thispinches the impacted sidewall severely which can result in cut ordamaged carcass plies. Repeated landings result in cumulative damage. Toextend the life of the main tire additional full width carcass plieshave been used; however, this imposes a weight penalty.

The present invention discloses a novel approach to improve sidewalldurability while enabling a reduction in overall tire weight.

SUMMARY OF THE INVENTION

An improved aircraft tire having a tread portion 12, a pair of sidewallportions 14, 16, a pair of spaced apart bead portions 18, 20 having atleast one, preferably two or three inextensible bead cores 50, 52, 54disposed side-by-side and spaced apart axially, and a plurality ofcarcass plies 36, 37, 38, 39, 40, 41 extending circumferentially aboutthe tire 10 from bead portion 18 to bead portion 20 is described. Eachply has a ply side extending between the bead cores 50, 52, 54 ofopposite bead portions.

The improved tire 10 has at least one circumferentially extendingreinforcement insert 90. At least one reinforcement insert 90 is locatedon one or on both sides of the tire 10. The reinforcement inserts 90extend from the bead portion 18, 20 and terminate in a radially upperportion of the sidewall 14A, 16A. Each insert 90 is interposed betweenthe carcass plies and the sidewall.

Preferably, the reinforcement insert 90 consists of a pair of axiallyadjacent cord reinforced members 91, 92, each cord reinforced member 91,92 having bias angled cords, the cords being equal but opposite inorientation relative to the cords of the adjacent member. The pair ofcord reinforced members 91,92 preferably have an elongation at breakunder load similar to the adjacent carcass plies 36, 37, 38, 39, 40, 41.Preferably, the cords of the ply and the reinforced member 91, 92 arethe same; and more preferably, the cords are textile cords such as nylonor aramid cords. Alternatively, the reinforcement insert 90 can be anelastomeric material containing fiber reinforcement.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view illustrating the improved aircraft tiremade in accordance with the present invention;

FIG. 2 is a further enlarged cross-sectional view illustrating one sideor half of a tire made in accordance with the present invention;

FIG. 3 is a schematic view of one half of the tire showing the ply,insert, and bead core orientation;

FIG. 4 is cross-sectional view illustrating a second embodiment tiremade in accordance with the present invention.

DEFINITIONS

"Apex" means a non-reinforced elastomer positioned radially above a beadcore.

"Aspect ratio" of the tire means the ratio of its section height (SH) toits section width (SW) multiplied by 100% for expression as apercentage.

"Axial" and "axially" means lines or directions that are parallel to theaxis of rotation of the tire.

"Bead" means that part of the tire comprising an annular tensile memberwrapped by ply cords and shaped, with or without other reinforcementelements such as flippers, chippers, apexes, toe guards and chafers, tofit the design rim.

"Belt or breaker reinforcing structure" means at least two layers ofplies of parallel cords, woven or unwoven, underlying the tread,unanchored to the bead, and having both left and right cord angles inthe range from 17 degrees to 33 degrees with respect to the equatorialplane of the tire.

"Bias ply tire" means a tire having a carcass with reinforcing cords inthe carcass ply extending diagonally across the tire from bead core tobead core at about a 25°-50° angle with respect to the equatorial planeof the tire. Cords run at opposite angles in alternate layers.

"Carcass" means the tire structure apart from the belt structure, tread,undertread, and sidewall rubber over the plies, but including the beads.

"Circumferential" means lines or directions extending along theperimeter of the surface of the annular tread perpendicular to the axialdirection.

"Chafers" refers to narrow strips of material placed around the outsideof the bead to protect cord plies from the rim, distribute flexing abovethe rim, and to seal the tire.

"Chippers" mean a reinforcement structure located in the bead portion ofthe tire.

"Cord" means one of the reinforcement strands of which the plies in thetire are comprised.

"Equatorial plane (EP)" means the plane perpendicular to the tire's axisof rotation and passing through the center of its tread.

"Flipper" means a reinforced fabric wrapped about the bead core andapex.

"Footprint" means the contact patch or area of contact of the tire treadwith a flat surface at zero speed and under normal load and pressure.

"Innerliner" means the layer or layers of elastomer or other materialthat form the inside surface of a tubeless tire and that contain theinflating fluid within the tire.

"Net-to-gross ratio" means the ratio of the tire tread rubber that makescontact with the road surface while in the footprint, divided by thearea of the tread in the footprint, including non-contacting portionssuch as grooves.

"Nominal rim diameter" means the average diameter of the rim flange atthe location where the bead portion of the tire seats.

"Normal inflation pressure" refers to the specific design inflationpressure and load assigned by the appropriate standards organization forthe service condition for the tire.

"Normal load" refers to the specific design inflation pressure and loadassigned by the appropriate standards organization for the servicecondition for the tire.

"Ply" means a continuous layer of rubber-coated parallel cords.

"Radial" and "radially" means directions radially toward or away fromthe axis of rotation of the tire.

"Radial-ply tire" means a belted or circumferentially-restrictedpneumatic tire in which the ply cords which extend from bead to bead arelaid at cord angles between 65° and 90° with respect to the equatorialplane of the tire.

"Section height" (SH) means the radial distance from the nominal rimdiameter to the outer diameter of the tire at its equatorial plane.

DETAILED DESCRIPTION OF THE INVENTION

With reference to FIG. 1, there is illustrated a tire 10 which in thespecific embodiment illustrated is a size 32×11.5-15 tire. The tire hasa 81.3 cm (32 inch) maximum inflated outside diameter and the maximumwidth of the inflated tire in the axial directions is 29.2 cm (11.5inches) and the tire has a nominal bead diameter of 38.1 cm (15 inches).

The tire 10 includes a ground engaging circumferentially extending treadportion 12, a pair of sidewalls 14, 16 extending radially inwardly fromthe axially outer edges of the tread portion and terminating at theirradial extremities in a pair of bead portions 18, 20. The sidewalls 14,16 each have an upper portion 14A, 16A in the shoulder region of thetire radially inward of the tread and radially outward of the maximumsection width of the tire, and a lower portion 14B, 16B radially inwardof the maximum section width of the tire. A cord reinforced carcassstructure 22 extends circumferentially about the tire from bead portion18 to bead portion 20.

The particular embodiment of the cord reinforced carcass structure 22includes six pairs of plies of tire cord fabric 36, 37, 38, 39, 40, and41. Each pair of plies has one of its plies extending at one bias anglewith respect to the equatorial plane or circumferential center line ofthe tire, and the other ply at the same angle but extending in theopposite direction with respect to the equatorial plane. The angle thatthe cords in the individual carcass plies make with respect to theequatorial plane decreases progressively from an angle of about 34° inthe radially inner pair of plies 36° to 30° in the radially outer pairof plies 41.

Also included in the carcass structure is a pair of tread breaker plies44 extending circumferentially about the carcass and generally from oneedge of the tread portion 12 to the axially opposite edge of the treadportion 12. The angle of the cords in the tread breaker plies withrespect to the equatorial plane is approximately 26°. The material ofthe cords in all of the plies in the carcass structure 22 is nylonalthough any suitable material or combination of materials can beutilized. It is believed preferable that the cords be a textilematerial. Further, while specific angles have been specified for thecarcass and tread breaker plies, these angles can be varied within thenormal range of bias ply aircraft tires. For example, the angles of thecarcass plies could be from 25° to 45° while the angle of the treadbreaker plies can be from about 20° to 45° for a bias ply aircraft tire.

Interposed between the tread breaker plies 44 and the carcass plies is acushion gum layer 19.

The bead portions 18, 20 each include three annular inextensible beadcores 50, 52 and 54.

Two pairs of carcass plies 36 and 37 extend radially inwardly of thetire adjacent to the axially inner side of the axially inner bead core50. The respective ends 36a and 37a are turned axially outwardly aboutbead core 50 and ply ends 37a are turned radially outwardly about beadcore 50 while ply ends 36a turn radially outwardly about bead core 54.

Carcass plies 38 similarly extend radially inwardly adjacent to theaxially inner side of the central or middle bead core 52 and have theirends 38a turned radially outwardly of the bead core 52.

Carcass plies 39 extend radially inwardly about the axially outer sideof the middle bead core 52 and the ply ends 39a are turned axiallyinwardly adjacent the radially inner sides of the inextensible beadcores 50 and 52. Since the pairs of carcass plies 39 are wrapped abouttwo sides of the bead core 52 as they progress radially inwardly fromthe tread 12, the tensile loading of these plies caused by inflationpressure and loading on the tire are supported by bead core 52.

The axially outer bead core 54 has a pair of carcass plies 40 extendingradially inwardly adjacent the axially inner side of the bead core andhas its ends 40a turned axially outwardly adjacent the radially innerside of the bead core. The turnup ends 40a turn radially outwardlyadjacent the axially outer side of the bead core 54.

Carcass plies 41 extend radially inwardly interposed between the turnupends 36a and the axially outer side of the bead core 54. The carcass plyends 41a each turn axially inwardly adjacent the radially inner side ofbead core 54 extending inwardly to the radially inner side of bead core50. The ends 41a is interposed between the bead cores 50, 52 and 54'sradially inner sides and the ends 36a. The ends 36a terminate in thelower sidewall area at a point radially inwardly of the point 62 ofmaximum section width of the inflated tire.

For the purposes of this invention, end portions shall be those portionsof a carcass ply pairs that wraps about or extends radially outwardlyfrom a bead core. If the end portions terminate short of the point 62 ofmaximum axial width of the tire, it is not considered working portionsof the plies since it does not exert a significant radially outwardlydirected pull on the bead core. A bead core that absorbs a majorradially outwardly directed pull of the carcass plies is an active orworking bead core, and for purposes of this invention is a bead corebounded on any axial side and a radially inner side by the workingportions of the carcass plies. The working portions of the carcass pliesis that portion of the plies extending from a bead on one side of thetire to the opposite side's bead, and for purposes of this invention theworking portion of the carcass plies is called the ply side; thenon-working portion is the turn-up or end portions of the plies.

Referring to FIG. 2 of the embodiment illustrated, a group of structuralcomponents employed in the tires is shown.

Radially above each bead core 50, 52, 54 is an elastomeric apex 57.Wrapped about each bead core and axially adjacent each apex is a flipper55. Wrapped about the entire bead structure is a chafer 56. The chafer56 extends radially inwardly from an axially outer end toward the beadheel 59, turns axially inwardly extending to the bead toe 58 where thechafer 56 turns radially outwardly to an axially inner end. In theembodiment as illustrated, the air chamber formed by the tire issurrounded by a generally air impervious innerliner 17 extending frombead to bead.

As illustrated in FIGS. 1 and 2, and shown in schematic FIG. 3, areinforcement insert 90 is radially outward of the pair of plies 40, 41.As shown, the inserts 90 are positioned on the radially outer side ofthe plies and extend from adjacent or slightly above the bead coresradially and axially outwardly to a radially outer end below the tread12 in the upper sidewall 14A, 16A region between the carcass 22 and thesidewall.

In the best mode of practicing the invention, the reinforcement inserts90 consist of a pair of cord reinforced members 91, 92. The cords in thereinforced members 91, 92 are at bias angles relative to thecircumferential center line, the cord angle of one member of a pairbeing equal to but opposite in orientation relative to the cords of theadjacent member of the same pair.

It is believed preferable that the insert cords have a tensileelongation at break substantially similar to the nylon cord of theplies. For that reason, the cords in the preferred embodiment were madeof nylon. Alternatively, the cords could be any other suitable textiletype material.

It is believed that the reinforcement insert 90 could be fabricated froman elastomeric material having fiber reinforced materials.

In the preferred embodiment the reinforcement insert 90 extendscircumferentially around the tire 10 on only one side. The purpose ofthe reinforcement insert 90 is to increase the carcass 22 lower to uppersidewall impact durability with a corresponding decrease in weight whencompared to conventional bias ply aircraft tires. The carcass impactstrength is increased by locating impact absorbing reinforcement inserts90 in the sidewall 14, 16.

In a first use of the invention as illustrated in FIG. 1, the inserts 90were fabric plies 91, 92 having the same green angle as the adjacentfull casing plies. The insert fabric plies 91, 92 were located in thetire 10 in pairs, one fabric member 91 oriented at an angle left and onefabric member 92 at an equal angle right. One such two-ply fabric insert90 was located adjacent the axially outer side of the bead core 54 andextended radially outwardly to the upper sidewall portion 16A. Theinserts 90 were located radially outward of the full band plies and hadthe radially inner ends purposely terminated such that the insert endsdid not extend around the bottom of the bead 54.

Although one set of inserts 90 per tire side was contemplated in theearly evaluation of this invention, it was determined that one set onone side was sufficient in the application being evaluated. One, two,three or four sets of inserts 90 per tire side can be used, depending onhow much additional carcass impact strength is required.

Although the inserts 90 were used having pairs of bias angled cordreinforced members 91, 92, it is believed that the cord reinforcedmembers 91, 92 can be individually used. Also in the above description,the cord reinforced members had bias angles in the same range as thecarcass plies. Alternatively, higher angles up to 90° could be used.

Historically, bias ply aircraft tires have been designed with full widthcarcass plies, which extend from a bead bundle on one side of the tireto the bead bundle on the other side of the tire. In order to increasecarcass strength in any one area of the tire, it was common practice toadd full width plies to the carcass. The present invention, by addingfabric or fiber inserts between the plies and the sidewall of the tire,strengthens only the area requiring the impact strength increase. Sincefull plies are not used, there is a substantial tire weight savings.

An aircraft tire 10 built in accordance with the present invention asshown in FIGS. 1, 2, and 3 was tested against standard productionaircraft tires for impact durability. The standard or control tire wassize 32×11.5-15 and the test tire 10 was made of the same materials andof similar construction as the standard tire, except for the addition ofthe fabric reinforced insert plies 91, 92 on the non-serial numberedside. The test tire 10, according to the present invention, exhibited amarked improvement over the impact durability of the standard tirewithout inserts.

In a tire 10 built according to the present invention and for use in anaircraft currently in development as illustrated in FIGS. 1-3, anincrease in durability was achieved using only one insert 90 on one sideof the tire. A standard tire with the same number of full plies as thetest tire but without inserts was evaluated. It failed the impactdurability test. This standard tire had a weight of 67 pounds. The tireaccording to the invention passed the test and had weight of 68.1pounds. To achieve the same level of sidewall impact durability usingtwo additional conventional full ply pairs a tire weight of 73.4 poundswould result. As can be seen above, significant impact durabilityimprovements can be achieved without the normal weight penaltyassociated with the use of additional full width plies.

One of the most rigorous requirements of the MacDonald Douglas F/A-18E/Fbias main aircraft tire is for the tire 10 to survive the 1-5/8"diameter cable load test being more than 5 times rated tire load appliedat a camber angle of 10.2 degrees. This severe test pinches the tiresidewall between the wheel and the cable on one side of the tire whichcan result in the cutting of the carcass plies and if excessive, cancause a failure of the tire structure.

To protect the tire carcass 22 in the sidewall area from such anoperation, two layers of fabric 91, 92 starting from the tire shoulderarea 16A to just above the bead area 20 were inserted between the tirecarcass 22 and sidewall 16. The two layers 91, 92 are of the samematerial and ply angle as the carcass plies and are offset 0.5" to avoidhigh stress concentration at the layer edges. The carcass material is1260/2 nylon.

For the F/A-18 E/F aircraft, the worst case landing (combination oflanding gear geometry and aircraft position) would be (non-serial sideof tire facing towards the center of the aircraft). Because of this,there is no need to have the two layers of fabric on the serial of thetire 10. This results in an asymmetric tire carcass design.

If tire weight was not an issue, adding full width carcass plies to thetire would be sufficient to protect the tire carcass from the severecambered cable bruise test.

The tire 10 described in this invention allows the tire to be optimizedby adding layers of inserts only where it is needed, that is, two layers91, 92 of fabric starting from the tire shoulder area to just above thebead area.

The radially outer ends of the insert 90 terminates radially below thetread portion 12 in the upper shoulder region of the tread. Preferably,the radially outer ends of the insert 90 are at least about halfwaybetween the point 62 of maximum section width and the axial end of thetread portion 12. When the insert 90 is composed of two fabric plies 91,92, it is preferred that the end of each ply is slightly staggered asillustrated in FIGS. 1, 2 or 3.

In application where the impact can strike either sidewall or both. Itis believed that an insert 90 should be employed on both sides of thetire 10 thus forming a symmetrical carcass configuration as shown inFIG. 4.

Although the invention illustrates and describes the use of inserts onbias aircraft tires having at least two bead cores on each side of thetire, it is believed feasible to employ the inserts as described aboveon radial ply aircraft tires having only one bead per tire side.

What is claimed:
 1. An aircraft tire having a tread pattern, a pair ofsidewall portions, a pair of spaced apart bead portions having at leastone extensible bead core disposed side by side and spaced apart axially,and a plurality of carcass plies extending circumferentially about thetire from bead portion to bead portion, each ply being cord reinforcedand having a ply side extending between the bead cores of opposite beadportions, the improvement comprising:at least one circumferentiallyextending reinforcement insert on each side of the tire, thereinforcement insert or inserts extending from the bead portion andterminating in a radially upper portion of the sidewall portion, eachreinforcement insert or inserts being radially outward of the carcassplies and interposed between the sidewall portion and the carcass plies,the reinforcement insert or inserts having a pair of axially adjacentcord reinforced members, and wherein the cords of the carcass plies andthe cords of the reinforced members are the same.
 2. The aircraft tireof claim 1 wherein the cord reinforced members have bias angled cords,the cords being equal but opposite in orientation relative to the cordsof the adjacent cord reinforced member.
 3. The aircraft tire of claim 1wherein the pair of axially adjacent cord reinforced members of thereinforcement insert or inserts have radially extending cords.
 4. Theaircraft tire of claim 1 wherein the cords of the carcass plies and thecords of the reinforced members are nylon.
 5. The aircraft tire of claim1 wherein the tire has two reinforcement inserts per tire side.
 6. Theaircraft tire of claim 1 wherein the tire has three reinforcementinserts per tire side.
 7. The aircraft tire of claim 1 wherein the tirehas four reinforcement inserts per tire side.